George M. Reisner

Studies on metal—metal bonds ☆: II. The crystal and molecular structures and other physical properties of (η5-C5H5)2Co2(NO)2−x(CO)x (x = 1, 0). A comment on the ean rule

Abstract The compounds (η 5 -C 5 H 5 ) 2 Co 2 (NO) 2− x (CO) x ( x = 1, 0) crystallize in space group P 2 1 / c with Z = 2 molecules per unit cell. The unit cell constants for the former ( x = 1) are: a 7.878(5), b 6.121(1), c 12.080(4) A and β 105.46(2)°; while those for the latter ( x = 0) are: a 7.883(1), b 6.117(1), c 12.119(3) A and β = 105.44(2)°. In both cases the fragment Co-μ 2 -(NO) 2− x (CO) x Co is planar, with a maximum deviation of any atom in that fragment from its least squares plane of 0.004 A. The Cp rings are planar and have normal CC distances. The perpendiculars to the Cp planes make angles of 90° with the normals to the Co(NO) 2− x (CO) x Co planes. In what followes the values given in parentheses refer to the x = 0 derivative, the other values refer to the carbonylnitrosyl derivative ( x = 1). The range of CoC(Cp) distances is 2.071 to 2.103 A, mean 2.088 A (2.086 to 2.115 A, mean 2.101 A). The Cp ring CC distances range from 1.379 to 1.401 A, mean 1.388 A (1.381 to 1.445 A, mean 1.411 A). The CoN (or C) distances are 1.829 and 1.831 A (1.824 and 1.827 A). The NCoN (or C) angle is 99.3° (99.0°). The two independent values of the CoN (or C)O angles are 139.5 and 139.8° (139.4 and 139.6°) while the value of the CoN(or C)Co angle is 80.7° (81.1°). The CoCo distance is 2.370 (2.372) A. The EAN rule is discussed with regard to these and related observations. The paramagnetic carbonylnitrosyl derivative gives a 15 line ESR spectrum (room temperature, benzene) of which the lines have, approximately, intensity ratios of 1/2/3⋯7/8/7⋯3/2/1, expected for an unpaired electron distributed equally over two 59 Co nuclei. The 59 Co hyperfine splitting is 47.4 Oe, the g value is 2.0539 and the linewidth is ca. 29 Oe. At room temperature there is no evidence of a 14 N hyperfine splitting from the bridging nitrosyl.

Solid state structure and reactivity in solution. The crystal and molecular structures of (OC)4W(t-BuS(CH2)nS-t-Bu) (n = 3, 2)

Abstract The crystal and molecular structures of the compounds having composition (OC)4W(t-BuS(CH2)nS-t-Bu) (n = 3,2) were determined from single crystal X-ray diffraction data collected with a computer controlled diffractometer, using Mo-Kα radiation. The data that follow are given in the order n = 3 first, followed by the relevant data for the derivative with n = 2. Space group, P212121 and cell constants: a 9.388(4), b 9.548(2), c 21.989(11) A; D(calc) 1.74 g cm−3 and Z 4 molecules per unit cell. Space group C2/c and cell constants: a 25.568(9), b 8.958(3), c 16.457(2) A and β 95.810(13)°; D(calc) 1.78g cm−3 and Z 8 molecules per unit cell. Both structures were solved by Patterson methods using data corrected for absorption. Final refinements converged to R(F) factors of 4.6 and 6.3%, respectively, for (n = 3 and 2). The W—S distances when n = 3 are 2.574(5) 3.284(7) A. When n = 2, W—S distances are 2.559(5) and 2.565(4) A, the S—W—S angle is 80.8(1)° and the non-bonded S…S distance is 3.323(6) A. Both molecules contain octahedrally distorted WC4S2 fragments which are quite similar in their geometrical details. The overall WC4S2 fragments are normal and their structural characteristics compare well with established values. Comparisons between the structural data and reactivity via ligand exchange (replacement of the bidentate ligand) suggest that observed small but statistically significant differences in molecular geometries for the two complexes exert an appreciable cumulative effect upon reactivity.

Solid state structure and reactivity in solution. 8. Implications of the structure of [1,2-bis(diphenylphosphino)ethane] tetra-carbonylmolybdenum(0) to the chelate effect

Abstract The structure of (diphos)Mo(CO)4 (diphos=1,2- bis(diphenylphosphino)ethane) has been determined by single crystal X-ray crystallography. The crystals are orthorhombic with a=22.600(8), b=16.799(4) and c=14.587(4) A, space group Pbca, Dcalc.=1.45 g cm−3 and Z=8. The structure was solved by the Patterson technique and refined by full-matrix least- squares methods to R=0.044 using 2206 reflections measured on a four-circle diffractometer. The coordination about the central molybdenum atom is a distorted octahedron, the greatest deviation from ideal geometry being the P1-Mo-P2 angle (80.2(1)°). Other distortions are induced through steric interaction between the phenyl and the carbonyl groups. The structure of (diphos)Mo(CO)4 is compared to that previously reported for cis- (MePh2P)2Mo(CO)4; the two molecules differ only that two methyl groups of the latter complex are replaced by the CH2CH2 backbone in the former. The influence of this difference is discussed both in terms of molecular distortions induced by the presence of the chelate ring and their influence on reactivity via chelate ring-opening and -closure.

SOLID STATE STRUCTURE AND REACTIVITY IN SOLUTION. II. THE CRYSTAL AND MOLECULAR STRUCTURE OF (2,2,7,7-TETRAMETHYL-3,6-DITHIAOCTANE)TETRACARBONYLCHROMIUM(0)

The crystal and molecular structure of the title compound, (DTO)Cr(CO) 4 , has been determined by single-crystal X-ray diffraction techniques. The crystals are monoclinic, a = 9.583(4), b = 13.399(5) and c = 14.809(8) A , β = 101.62(4)°, space group P2 1 /n, d (calc. z = 4) = 1.32 g/cm 3 . The structure was solved by MULTAN and refined by full-matrix least-squares methods to R = 0.05 using 2274 reflections measured on a four circle diffractometer with Mo-Kα radiation. The coordination about the central chromium atom is a distorted octahedron, the greatest deviations from ideal geometry being the angle S1CrS2, 80.6(1)°, and the angle between the two mutually trans carbonyls, 169.8(2)°. Mean metal-ligand bond lenghts are CrS = 2.437(1), CrC( cis ) = 1.863(5) and CrC( trans ) = 1.820(5) A . The influence of the two bulky t-butyl substituents, bonded to S, on the octahedral geometry about Cr, and the possible influence of this molecular distortion on the reactivity of the complex via displacement of the chelating ligand by Lewis bases are discussed.

The absolute configuration of organometallic compounds : VII. An x-ray structural study of (−)579436-(η5-C5H5)Mo(CO)2[(C5H5N)C(=S)NR] prepared from H2NR = (S)-(−)-α-phenylethylamine

The reaction of (η 5 -C 5 H 5 )Mo(CO) 3 Cl with pyridine-2-carboxylic acid [( S )-1-phenylethylthioamide] yields two diastereoisomers having composition (η 5 -C 5 H 5 )Mo(CO) 2 (thioamide) which are in equilibrium with one another in the ratio of 58/42 (toluene; 90°C). The diastereoisomers are separable by chromatography, and that (V; see text) whose CD spectrum shows (−) and (+)-bands, respectively, at 579 and 436 nm was used in the current crystallographic study. The space group is P 2 1 2 1 2 1 and the cell parameters are: a 6.950(4), b 14.038(4) and c 20.709(8) A; V 2020.4 A 3 ; d (obs; flotation in aqueous ZnBr 2 ) 1.51 g cm −3 ; d (calc; Z = 4) 1.507 g cm −3 . A total of 3321 data were recorded in one octant of reciprocal space (2θ max 60.0°) of which 2134 were considered observed ( I > 2σ( I )) and used in the solution of the structure and in the least-squares refinement. The molecules consist of a central Mo atom surrounded by an approximately square-pyramidal array of five ligands: the bidentate thioamide, two carbonyls and the Cp ring. The binding points of the thioamide are the nitrogen of the pyridine and the sulfur of the thioamide moiety. Thus, unlike previous examples of CpMo(CO) 2 (thioamides) studied here, the nitrogen of the thioamide is not part of the chelate ring; instead, it is part of an unusual, three atom, conjugated system (SCN) never observed before in thioamide-metal chelates. The SMoN, SMoC(O), NMoC(O) and (O)MoC(O) angles are 76.9(2), 75.2(3), 81.4(4) and 75.6(5)°, values which are typical of square-pyramidal compounds in which the metal is above the plane defined by the basal ligands. The bonds to the carbons of the C 5 H 5 ring are normal but the two MoC(O) and the two CO distances are slightly different, and the differences make sense if we attribute them to inequalities in trans effect between S and N ligands opposite the carbonyls. The MoN(pyridine) bond (2.233(8) A) is a little longer than those observed in thioamides but nearly the same as that observed in Schiff base derivatives of related CpMo(CO) 2 compounds studied here earlier. Concomitantly, in V there is a shorter MoS bond than those observed in the thioamides containing normal, four-membered (MoSCN) chelate rings. Parallel with this, V contains longer SC bonds showing that an increase in the MoS bond order leads to a reduction of the SC π-bond order, which in this case is estimated to be only 0.47. Finally, the plane of the chelate ring (MoSCCN) and that of the pyridine ring make an angle of 8.7°, even though the two are fused to each other. The absolute configuration at the Mo site of the [(−) 579 , (+) 436 ] diastereoisomer has been established as ( S ).

On the absolute configuration of organometallic compounds : VIII. A comparison of the structural characteristics of racemic and of (−)578-(η5-C5H5)Mo(CO)2SC(CH3NR with R CH[CH(CH3)2](C6H5) and (S)-CH[CH(CH3)2](C6H5)

Abstract The crystal structures of one of the diastereoisomers and of the racemic pairs having composition (η5-C5H5)Mo(CO)2SC(CH3)NR with R = CH[CH(CH3)2]-(C6H5) have been determined from single crystal X-ray diffraction data. The results that follow are given first for the active and then for the racemic crystal: Space group P21, a = 9.366(2), b = 16.199(3), c = 12.722(1) A, β = 99.399(8)°, d(calc.) = 1.477 gm cm−3 and z = 4 molecules/unit cell; Space group P21/n, a = 9.111(2), b = 12.774(4), c = 16.465(4) A, β = 94.81(2)°, d(calc.) = 1.472 gm cm−3 and z = 4 molecules/unit cell. Refinement for the two crystals converged to R(F) = 0.020, Rw(F) = 0.021 and R(F) = 0.073, Rw(F) = 0.075. The Bijvoet test was applied to the enantiomorphic crystal and the configuration assigned is (S) for both the optically active carbon and the Mo site. Both compounds have an approximately square-pyramidal configuration around the Mo atom in which the thioamide ligand is bound through the S and N atoms. This attachment of the thioamide ligand has only recently been structurally documented. The conformation of the molecules is nearly identical for all the compounds described in this study, as well as for similar species previously reported. Finally, the packing of the enantiomer and of the racemic pair is different. In spite of that, the density is nearly identical for the two substances.

On the cyclodimerization of acetylenes to cyclobutadiene problem: the synthesis, crystal and molecular structure of (η5-cyclopentadienyl)-(η4-1,2-diphenylcyclobuta[l]phenanthrene)rhodium

Abstract A reaction between 2,2′-bis(phenylethynyl)biphenyl and η5-cyclopentadienylcarbonylrhodium has been found to produce several organometallic products, including (η5-cyclopentadienyl)(η4-1,2-diphenylcyclobuta[l]phenanthrene)rhodium has been determined by single-crystal X-ray diffraction using data acquired by a computer-controlled diffractometer. The substance crystallizes in the triclinic system, space group P 1 , with cell constant of a 10.023(1), b 11.146(3), c 22.314(4) A, α 101.26(2), β 97.53(1) and γ 96.55(1)°. The observed and calculated densities (for two molecules in the asymmetric unit) are 1.45(1) and 1.446 g/cm3, respectively. The structure was solved by Patterson, Fourier and least-squares refinement techniques. Final discrepancy indices are R(F) - 3.6% and Rw(E) = 4.2%. The (η5-C5H5)Rh fragments have a normal disctances and angles, the Cp rings being planar as expected. The cyclobutadiene rings are also planar (largest deviations from planarity being 0.003 A) and parallel to the Cp rings. The most important change, as a result of the constraints of the fused cyclobuta[l]phenanthrene system, is the trapezoidal shape of the (η4-C4) ring. The effects of fusion and of strain, caused by the crowding of two hydrogen atoms at the open side of phenanthrene, on the cyclobuta[l]-phenanthrene system are discussed.

Crystal structures of phenyl-substituted cyclopropanes. IV. the crystal structure (at 21‡C and −100‡C) and the phenyl ring conformation in 4-cyclopropylacetanilide

The crystal structure of 4-cyclopropylacetanilide was investigated at room temperature (21‡C) and at −100‡C in order to determine the orientation of the phenyl ring with respect to the cyclopropane moiety and the effect of this substituent on the stereochemistry of the three-membered ring. The compound was chosen because it is one of the few species containing a simple phenyl ring as the sole cyclopropane ring substituent and whose crystals are suitable for X-ray diffraction at room temperature. The substance crystallizes in space groupP2l/c at either temperature (no phase transitions) with cell constants: (at 21‡C)a=9.725(2),b=10.934(3), andc=9.636(2) å,Β=106.13(1)‡;V=984.21 å3 andd(calc;z=4)=1.182 g cm−3. The relevant parameters for the −100‡C structure area=9.557(4),b=10.980(2), andc=9.641(2) å,Β=106.34(3)‡;V=970.76 å3 and d(calc;z=4)=1.199 g cm−3. Final values wereR(F)=0.042, Rw=0.035, using unit weights, and its nonhydrogen atoms were used to phase the low-temperature data, whose final discrepancy indices wereR(F)=0.051,Rw=0.061. The phenyl substituent is almost exactly in the bisecting conformation with respect to the C-C-C angle at the point of attachment to cyclopropane and conjugative effects are clearly evident in the lengths of the cyclopropane ring [1.494(3), 1.498(3), and 1.474(4) å, the later being the distal bond]. If one omits the terminal methylene fragments at C10 and C11, the atoms comprising the acetanilide fragment and the substituted carbon of the cyclopropane ring lie in a nearly perfect plane. Molecular mechanics as well as semiempirical (AM1) calculations were carried out in order to determine the structure of the energy-minimized configurations in the two computational environments. The molecular conformations thus obtained are close to that experimentally observed from the X-ray diffraction experiment. In both theoretical models, the lowest energy conformation is that in which the plane of the phenyl ring bisects the cyclopropane C-C-C angle as was experimentally observed. Finally, the shape of the conformational barrier as a function of the orientation of the plane of the phenyl ring was computed, giving a maximum barrier to rotation of 2.2 kcal/mol. Similar calculations were carried out for two other aryl cyclopropanes, whose rings (naphthalene and anthracene) cannot adopt the bisecting position. Comparisons of experimental geometrical parameters as well as of the barriers to rotation are presented.

Crystal structures of chromium(III) fluoride trihydrate and chromium(III) fluoride pentahydrate: structural chemistry of hydrated transition metal fluorides. Thermal decomposition of chromium(III) fluoride nonahydrate

The crystal structures of the green compounds CrF3 · 3 H 2 0 and CrF3 · 5 H 2 0 have been determined. The first is rhombohedral [aR = 5.668(4) Ä, ocR = 112.5(1)°, space group Rl>m, Ζ = 1] and the second orthorhombic [a = 10.396(5), b = 8.060(5), c = 7.965(4) Ä, space group Pbcn, Ζ = 4], Both compounds contain the same octahedral molecules Cr[F3(H20)3], but the nature of the isomers present could not be determined because of crystal disorder. There is extensive hydrogen bonding in both types of crystal. It has been found that violet Cr[H20]6F3 · 3 H 2 0 decomposes thermally to green Cr[F3(H20)3] in three stages, with violet Cr[H20]6F3 identified as the product formed in the first stage.

Optically active transition-metal compounds. Stereochemistry and crystal structure determination of [η5-C5H5)CoI-NC5H4C(R)NCH(CH3)(C6H5)]+I−, R = CH3 ☆ ☆☆

Abstract The crystal structures and absolute configurations of (η 5 -C 5 H 5 )-CoI(NC 4 H 3 -C(R)=N( S )-CH(CH 3 )(C 6 H 5 )) (R = H, compound I; R = CH 3 , compound II) have been determined by single crystal X-ray diffraction. Crystals of compound I are orthorhombic, with a 11.084(6), b 12.107(6) and c 13.121(7) A, space group P 2 1 2 1 2 1 and d (calcd, Z = 4) 1.69 g cm −3 The structure was solved by the Patterson technique and refined with use of full matrix least-squares methods to R ( F ) = 0.031 and R w ( F ) = 0.028. Compound II is nearly isomorphous and isostructural; a 11.246(6), b 11.923(6) and c 13.370(7) A, d (calc., Z = 4) 1.71 g cm −3 and was refined to the final agreement factors of R ( F ) = 0.044 and R w ( F ) = 0.035. The Co atom has a distorted tetrahedral coordination, with Co-I 2.595(2) for I and 2.607(2) A for II; Co-(η 5 -C 5 H 5 ring centroid) 1.681(4) and 1.703(5) A; Co-N(pyrrole) 1.905(9) and 1.885(9) A; Co-N(imine) 1.971(8) and 2.003(9) A, all the parameters being well within values found in the literature. The configuration around the chiral carbon of the phenylethylamine is S for both compounds, whereas the configuration around the metal is R in I and S in II. The different metal configurations in I and II have their origin in the two different substituents (R = H, CH 3 ) at the imine carbon atoms of the chelate ring, which induce completely different conformations of the ( S )-CH(CH 3 )(C 6 H 5 ) moiety in the two complexes. For both compounds the thermodynamically less stable isomer is enriched upon crystallization. Also, for compound I the solution and solid state conformations are almost opposite to each other, the conformation in the solid reflecting intramolecular interactions (phenyl/C 5 H 5 attraction).